Centrifugal machine stripper knife and controlling mechanism



June 4, 1963 B. G. cox 3,092,575

CENTRIFUGAL MACHINE STRIPPER KNIFE AND CONTROLLING MECHANISM Filed Dec. 9, 1959 2 Sheets-Sheet 1 INVENTOR. BRADLEY G. COX

ATTORNEYS FIG. 2

FIG. I

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United States Patent 3,092,575 CENTRIFUGAL MACHINE STREPPER KNiFE AND CONTRULLKNG MECI IANESM Bradley G. Cox, Saginaw, Mich, assignor to Baker Perkins Ind, Saginaw, Mich, a corporation of New York Filed Dec. 9, 1959, Ser. No. 85%,392 4 Ciaims. (Cl. 210-141) This invention relates to centrifugal machines, and particularly to batch type centrifuges for separating solids and liquids, and certain novel and useful improvements therein.

Batch type centrifugals normally discharge the solids collected on the peripheral wall of the separating basket at a time when the basket or drum is still revolving and, to accomplish this removal of caked solids, a stripper knife of the general type shown in expired Ter Meer Patent 1,925,121 is moved radially toward the peripheral wall of the drum by a pressure fluid operated cylinder or the like, at the end of the batch centrifuging cycle. Difficulty has been encountered in the separation of some materials because the peeling knife, or scraper, as the knife is also known, in successive peeling operations, moves radially to the same point with respect to the Wall of the basket which, for safetys sake, is about of an inch short of actual contact with the wall of the drum. Thus, a residual heel always remains on the inner peripheral surface of the drum, and, with repeated strokes of the knife in repeated batch operations, an impervious surface layer forms on this heel. Plastic materials of certain crystalline structure, and particularly those materials which have low melting points, tend to glaze or smear over after several cuts and, when this occurs, the liquid components cannot get through to the perforate basket wall and the machine must be stopped and held out of operation while the glazed residual heel is laboriously removed.

An attempt has been made to solve this problem by providing time rinses during the batching operation in which alcohol or the like is forced through the cake. However, alcohol is expensive to use and its recovery has been difiicult. Further, with some materials, time rinsing with alcohol or other solvents is not efiective.

The present invention contemplates mechanism for automatically varying the length of the stroke of the scraping or peeling knife in successive batch operations and it is an important object of the invention to provide practical and reliable mechanism for accomplishing this objective.

A further ditficulty encountered with centrifugal ma chines having peeler knives of the character to which I refer is the problem of air flow in a machine in which the chute for discharging the peeled solids leads outside the separator housing. With this chute or conduit open during the centrifuging operation, the separating basket tends to behave like a suction fan in that air is drawn through the solids discharge duct and expressed through the perforate basket with the liquid components, and the capacity of the machine is considerably decreased. With air flowing to the liquid outlet of the Wet housing also, the outflow of liquids from the wet housing is materially impaired because the liquid tends to spew out rather than proceed outwardly in an unobstructed, linear stream as it does when there is no air flow.

A further object of the invention is to provide a solids discharge chute and scraper knife box assembly which is designed to close and seal the discharge conduit when the scraper knife is not in operation.

Another object of the invention is to design a centrifugal machine in which the improved construction accomplishing the foregoing objectives is of simple and inexpensive design and the mechanism for varying the stroke of the 3 ,92,575 Patented June 4, 1963 peeling knife and for sealing the discharge chute, operates automatically.

A corollary object of the invention is to provide mechanism for varying the stroke of the peeling knife which, during a particular peeling operation, sets itself to operate with a different length stroke in the next operation.

Still a further object of the invention is to provide a mechanism of the character described which, because it automatically accomplishes the objectives outlined, need not depend on the memory or attention of an operator.

Other objects and advantages of the invention will be pointed out specifically or will become apparent from the following description when it is considered in conjunction with the appended claims and the accompanying drawings, in which:

FIGURE 1 is a fragmentary, front elevation-a1 view of the upper portion of the centrifugal machine, with the peeling knife shown in retracted position in broken lines, and upper or forward position in chain lines;

FIGURE 2 is a transverse, sectional view taken on the line 22 of FIGURE 1, with the scraper or peeler in retracted position;

FIGURE 3 is an enlarged, fragmentary view illustrating the control mechanism for varying the length of stroke of the peeling knife in more detail;

FIGURE 4 is a fragmentary, side elevational view of the control mechanism shown in FIGURE 3;

FIGURE 5 is an enlarged, top plan view taken on the line 55 of FIGURE 4 to illustrate a certain portion of the control mechanism;

FIGURE 6 is a view similar to FIGURE 4 with the parts shown in the position which they occupy when the scraper is in its upper position during a particular centrifuging operation.

FIGURE 7 is a transverse, sectional, plan view of the solids collection chamber assembly only taken on the line 77 of FIGURE 1, and

FIGURE 8 is a schematic view of a typical electrical system.

With the construction now to be described in detail, at least a considerably greater number of cycles can be run before the residual heel develops an impervious surface layer and the time consuming removal of the glazed heel becomes necessary, and in many instances it is found that, by varying the length of stroke, glazing which takes place at the most advanced stratum is partially, and sometimes completely, eliminated in succeeding batch operations because the knife does not immeditely return to that stratum.

Referring now more particularly to the accompanying drawings, a letter H generally indicates the housing of a centrifuging machine of the type shown in Ter Meer Patent 1,925,121, or Davis Patent 2,658,620. A revolvable shaft 10 journaled in a bearing Ill provided in the housing H as usual mounts the conventional basket or drum 12 within the wet housing chamber 13 of the centrifugal machine housing H, as shown. Formed in the rear wall 14 of the basket 12 is an inverted hub section 15 which receives the frusto-co-nioal end 10a of the shaft 10 and it will be seen that a coupling plate 16, fixed to the hub section 15, bolts to the section 1% of shaft 10 as at 17. At its opposite rear end, shaft 10 mounts a pulley or the like as in the aforementioned patent and an electric motor (not shown) can be provided for driving the shaft 10 at the desired speed of revolution.

The basket 12 includes the perforate, peripheral wall 18 which is provided with liquid expressing ports 19, and the front wall 20 of the basket has an opening 21 for receiving a solids collecting chute and knife box assembly generally designated C which, as will be disclosed, includes a knife box generally designated 22 and a discharge chute generally designated 23. The knife box 22 includes a sleeve portion 24 mounted for vertical reciprocation on a guide column or red 25 which is supported fast by a door D for the housing H. The sleeve portion 24 is connected by a coupling arm 26 forming part of the knife box 22 to a channel-shaped knife section 22 (FIG. 7) having a side wall 27 provided with a curvilinear top portion 27a (FIG. 1) which is sharpened as at 2717 to form a peeling edge. Front and rear walls 28 and 29 are provided and receive the similarly channel-shaped, but rcversely positioned, upper end section 3% of the discharge chute 23 which has a tubular lower section 30a leading out through the door D. The channel-shaped upper portion 30 of discharge chute 23, which has the tubular lower conduit portion 33a leading to a solids discharge receptacle or the like as in the aforementioned patent, has

- front and rear walls 30' and 39 and a side wall 31 forming one side wall of the solids-receiving chamber C. It Will be seen that the walls 27, 28 and 29 of the knife box 22 cooperate with the upper portion 30 (walls 30, 3t) and 31) of the discharge chute 23 to form the solids collecting chamber or assembly C leading to the tubular portion 3th: of discharge chute 23. At its upper end, wall 31 (see FIGURE 1) has a top wall portion 31a and it is important to note that when the knife box 22 is in lowered or retracted position the discharge chute 23 is closed to the basket 12. Side walls 36' and 39" are shaped to the wall portions 31a and 27a at their upper ends as are side walls 28 and 29 so that an tight seal is provided. 7

The door D, which mounts the guide column 25 in an upper end section 32 and also supports the knife box assembly 22, and discharge chute 23,. also mounts a fixed (relative to door section 32) pressure fluid operated cyl inder 33 which has an extending piston rod 34 threaded as at 35 to connect with the arms 24a on sleeve member 24. Housing H includes an annular flanged door frame portion 36 mounting a housing 37 for knife stroke indexing mechanism which will presently be described in detail, and it will be seen that the housing H has a seal ring 38 with a surface 38a cooperating with a similar annular surface 39 on the door 32 to seal the housing H when the door Dis fixed in closed position.

Provided on the guide sleeve portion 24 of the knife box assembly 22 is a rod member 40 which extends through an opening 41 provided for it in the upper end section 32 of door D, and mounted on the threaded upper end 49a of rod 40 is a switch-actuating blade 42, as shown, which is secured in adjusted position by nuts 43. The switch blade 42 is provided to actuate a multiple contact microswitch 44 of conventional design having a switch arm 45 fixed on a pivotal shaft 46, which arm 45, as will be seen, carries a roller member 47. As will later become apparent, when the arm 45 is forced downwardly by blade 42 and switch shaft 46 is pivoted clockwisely in FIGURE 4, contacts (to be later identified), in one of the two circuits connecting with the conventional, double acting, solenoid operated cylinder 33 are closed. Other contacts which will also be later identified and 0p e'rate to reverse the travel of the piston rod 34 when it has moved upwardly in a stroke of predetermined length are closed when the roller 47 is moved upwardly and shaft 46 is pivoted in the opposite direction.

Supported in predetermined position on the upper end 40a of the rod 40 by nuts 48 is a bar 49 having a transverse bore 50 snugly receiving a control shaft member 51. The shaft 51 is a friction lit in bore 50 in the sense that it does not pivot freely therein and some force is required to rotate the shaft 51 in the bore 50. It will be seen that a prismatic cam block 52 having cam faces a, b, c and d is fixed on the end of shaft 51 and a disk 53 having projecting pins 54 arranged at 90 intervals substantially radially opposite the corners of the cam block 52 (see FIGURE 6) is fixed on the opposite end of shaft 51. Each of the faces a-d is located at a different distance from the axis e of shaft 51, with face a being nearest axis e and face d being furthest from axis e. When face a is uppermost, the stroke of piston rod 34 and knife box 22 forwardly toward the wall 18 is greatest and the length of the stroke decreases as cam block 52 is successively moved counterclockwisely in FIGURE 6, in a manner to be described, and faces I), c and d are successively uppermost during the next three peeling operations.

Threaded in thersection 32 of door D is a bolt 55, secured by a nut 56, which serves as a cam actuating member. A guide bar 57 secured by screws 58 to a side wall of housing 37 also serves as a cam actuating memher, and further functions to maintain the position of the cam block 52 as it travels upwardly toward the switch roller 47. It is the projecting pins 54 which accomplish indexing of the cam 52 in a manner which will now be described. When the cam block 52 is in the position in which it is shown in FIGURE 6, with face a upward, the knife 22 has just completed its longest stroke and roller 47 has been moved upwardly by cam face a sufiiciently to make normally open switch contacts 59 (FIGURE 8) in a circuit 60 which includes cylinder (33) solenoid 61. The energization of solenoid 61 operates valves in cylinder 33 which feed fluid under pressure to the upper end of cylinder 33 and bleed it from the lower end of cylinder 33 so that the stroke of the piston rod 34 and knife box 22 is reversed and rod 40 moves downwardly. Since guide rod 57 terminates at its lower end above the level of disk 53 when disk 53 is near its lowermost position, disk 53, when near lowermost position, is free to be rotated. When the lowermost pin at the right side in FIGURE 6 comes into contact with bolt 55, the disk 53 is rotated counterclockwisely through approximately 45 and when one of the pins 54 subsequently engages the lower end of guide bar 57, the arc of rotation is completed. In FIGURE 4 the disk 53 is shown in lowermost position immediately after actuation by bolt 55 and just prior to assuming the position in which it is shown in FIGURE 6. When disk 53 was moved upwardly, the leftmost pin 54 in FIGURE 4 was engaged by the lower end of guide rod 57 and pivoted an additional 45 to dispose disk 53 in the position in which it is shown in FIGURE 6. Thereafter, because two pins 54 were in engagement with the guide surface 57, the cam 52 was locked in position with the surface a uppermost.

When disk 53 is in lowered position, as in FIGURES 3 and 4, normally open switch contacts 62 (FIGURE 8) in circuit line 63, which includes cylinder (33) solenoid 64, are closed by the switch blade 42 depressing roller 47. Consequently, when switch 65 is closed to make circuit 63, solenoid 64 will reverse the valves in cylinder 33 so that pressure fluid is fed to the lower end of the cylinder and bled from the upper end of the cylinder, and the knife box 22 will be moved upwardly. The conventional cylinder 33 can be a Bellows Electroaire cylinder as manufactured by The Bellows Company, of Akron, Ohio, and the switch 44 which has contacts 59 and 62 is also conventional and is manufactured by Micro Switch (10., a Division of Minneapolis-Honeywell Co, as their Model No. EX-XR3 switch.

The usual batch cycle comprises the consecutive steps of: charging the slurry, wet-spinning the slurry to remove the liquids through the ports 19 in the basket 12 and collect the solids on the inner surface of wall 18, washing the solids collected on the inner surface of wall 18 by spraying water or other cleansing liquids from a hose (not shown) extending into the drum 12, spin drying the washed solids, and thence spin peeling the solids from the inner peripheral wall of basket 12 and passing them through the chute 23 out the door D. Usually, the centrifugal machine is automatically cycled by a timing device and switch 65 which initiates the peeling operation will be automatically closed. However, normally open switch 65 could be a switch which is manually closed by an operator at the time it is desired to start the peeling operation.

It will be seen that the'upper end of casing 37 is open as at 66 to pass the rod 40a and switch blade 42 upwardly, and the front end of casing 37 is also open as at 67 so that when door D is swung outwardly about its hinge pin 68 (FIGURE 1) rod 40 and associated mechanism are free to move with the door. The hinge pin 68 is supported on the housing H and the door D has a hinge section 69 as shown in FIGURE A splash ring 70 is provided for keeping the slurry within the basket 12.

The operation of the machine should be apparent from the foregoing description. When switch 65 is closed, either automatically or manually, disk 53 is in the lowered position in which it is shown in FIGURE 4 and blade 4-2 is depressing switch arm 4-5 so that normally open switch 62 is closed. Thus, solenoid 64 is immediately energized and knife box 22 moves upwardly toward the peripheral wall 18 of the basket 12. Since the basket 12 is spinning at this time, the cakes of solids collected on the wall 18 are progressively stripped by the knife edge 27!) and fall into the chamber C formed by knife box section 22 and the upper section 36 of chute 23, and proceed downwardly through the lower section 30a of chute 23 and out to a solids collection receptacle outside the centrifugal machine. The chute 23 extends out through a sealed opening in the door D to communicate with the solids collection receptacle.

Cam 53 is pivoted through 45 when the leftmost pin 54 in FIGURE 4 meets the bottom edge of guide 57, as previously observed, which brings cam surface a into horizontal position. When cam surface a engages microswitch roller 47, normally open switch 59 in the microswitch 44- is closed and solenoid 61 is energized to reverse the travel of knife box 22. When the cam 53 moves downwardly sufficiently for the lowermost right hand pin to engage bolt 55, the cam 32 will be rotated through approximately 45 in a counterclockwise direction and blade 42 will close normally open switch 62 so that the mechanism is ready for the next peeling operation.

At the end of the next batch cycle when switch 65 is closed to commence the next peeling operation, cam 53 will again be pivoted through an additional 45 by the lower end of guide bar 57 and face b will be uppermost. The result is that the knife blade 27b will travel about of an inch less toward the inner periphery of wall 18 than it did in the previous peeling operation. Similarly, during the next cycle, face c will be uppermost and the stroke Will be A inch less than immediately previously, and when face is uppermost, in the next successive peeling operation, the knife box 22 will have its stroke of least length, which will be 3 of an inch less than its longest stroke.

The faces a-d can, of course, be arranged to provide any desired length of stroke, or variance therein, in any desired order. Further, multiple peeler knives could be used. When the knife 22 has returned to lowered position the surface 27a contacts wall 31a and the chute C is effectively and automatically sealed.

It should be apparent that the apparatus disclosed is of reliable and practical design and it is to be understood that the foregoing description is to be taken as illustrative rather than limiting and various equivalent mechanism may be employed within the scope of the subjoined claims.

I claim:

1. In a centrifugal separator particularly for segregating liquids and solids; a housing; a separating basket having a perforate, peripheral wall on which solids collect and through which liquids are expressed; means for rotating said basket; a scraper carrying arm in said basket movable generally radially in a path of travel toward and away from the said wall of the basket in an initial stroke; electric circuit means including source of power means;

motor means controlled by said electric circuit means for moving said scraper arm in said path; electric switch means, having actuatable switch element means in one position initiating movement of said motor means to move said scraper arm toward said wall and in another position initiating movement of said motor means to move said scraper arm away from said wall, connected in said circuit means; indexible means mounted to actuate said switch element means to one of said positions near one end of the stroke of said scraper arm; switch actuator means mounted to actuate said switch element means to the other of said positions near the opposite end of the stroke of said scraper arm; the switch means, and the indexible means and switch actuator means, being mounted by the arm and housing for relative movement; and means for automatically indexing said indexible means for varying the length of stroke of the scraper arm in additional strokes to vary the point at which the scraper reverses its travel toward said wall.

2. In a centrifugal separator particularly for segregating liquids and solids; a housing; a separating basket having a perforate, peripheral wall on which solids collect and through which liquids are expressed; means for rotating said basket; a scraper carrying arm in said basket movable generally radially in a path of travel toward and away from the said wall of the basket; electric circuit means including power source means; motor means controlled by said electric circuit means for moving said scraper arm in said path; a reciprocating element, mounting a cam member near its lower end, and having a switch actuator near its upper end, mounted on said scraper arm and moving therewith; electric switch means on said housing, having makeable and breakable contact means in one position initiating movement of said motor means to move said scraper arm toward said wall and in another position initiating movement of said motor means to move said scraper arm away from said wall, connected in said electric circuit means; said electric switch means being positioned in the path of travel of said cam member to be tripped thereby to initiate travel of said scraper arm in one direction and in the path of travel of said switch actuator to initiate travel of said scraper arm in the opposite direction; and means cooperable with said cam member and positioned in the path thereof, for adjusting the position of said cam member automatically during one stroke to vary the length of the next stroke of the scraper arm.

3. The combination defined in claim 2 in which said cam member is a revolvable polygonal cam, with multiple flat surfaces offset different distances from the axis of revolution thereof, and having an axially projecting pin thereon for each said flat surface on the cam; said means cooperable with said cam member including a member mounted on said housing in the path of one of said pins during a portion of the stroke of said reciprocating element.

4. The combination defined in claim 3 in which said means cooperable with said cam member includes also a member having a guide surface extending in the direction of the stroke in the path of one of the pins during another portion of the stroke and on which multiple pins bear during a portion of the stroke to positively hold the cam in adjusted position.

References Cited in the file of this patent UNITED STATES PATENTS 1,965,840 Jones July 10, 1934 2,271,493 Brewer Jan. 27, 1942 2,331,959 Buddeberg Oct; 19, 1943 FOREIGN PATENTS 346,428 Germany Dec. 30, 1921 430,385 Great Britain Jan. 18, 1935 

1. IN A CENTRUFUGAL SEPARATOR PARTICULARLY FOR SEGREGATING LIQUIDS AND SOLIDS; A HOUSING; A SEPARATING BASKET HAVING A PERFORATE, PERIPHERAL WALL ON WHICH SOLIDS COLLECT AND THROUGH WHICH LIQUIDS ARE EXPRESSED; MEANS FOR ROTATING SAID BASKET; A SCRAPER CARRYING ARM IN SAID BASKET MOVABLE GENERALLY RADIALLY IN A PATH OF TRAVEL TOWARD AND AWAY FROM THE SAID WALL OF THE BASKET IN AN INITAL STROKE; ELECTRIC CIRCUIT MEANS INCLUDING SOURCE OF POWER MEANS; MOTOR MEANS CONTROLLED BY SAID ELECERIC CIRCUIT MEANS FOR MOVING SAID SCRAPER ARM IN SAID PATH; ELECTRIC SWITCH MEANS, HAVING ACTUTABLE SWITCH ELEMENT MEANS IN ONE POSITION INITATING MOVEMENT OF SAID MOTOR MEANS TO MOVE SAID SCRAPER ARM TOWARD SAID WALL AND IN ANOTHER POSITION INITIATING MOVEMENT OF SAID MOTOR MEANS TO MOVE SAID SCRAPER ARM AWAY FROM SAID WALL, CONNECTED IN SAID CIRCUIT MEANS; INDEXIBLE MEANS MOUNTED TO ACTUATE SAID SWITCH ELEMENT MEANS TO ONE OF SAID POSITIONS NEAR ONE END OF THE STROKE OF SAID SCRAPER ARM; SWITCH ACTUATOR MEANS MOUNTED TO ACTUATE SAID SWITCH ELEMENT MEANS TO THE OTHER OF SAID POSITIONS NEAR THE OPPOSITE END 